Considering the circuit energy of communication systems, the energy efficiency of OAM-SM millimeter wave communication systems is analyzed and compared with the energy efficiency of conventional MIMO communication systems in the following. Assuming the transmit power is equally distributed among all transmission antennas, the power consumed by the multi-antenna transmitter is modelled as [1]}
\({\rho ^{{\text{total}}}} = {N_{\text{C}}}{\rho _{\text{C}}} + \alpha {N_{\text{C}}}\rho ,\qquad \mathrm {(41)}\) 
